R A D I A T I O N

PROTECTION

and the NRC

Radiation is all around us.

It is naturally present in our environment and has been since before the birth of this planet. Radiation occurs in nature, but it can also be pro- duced artificially, as in medical x-rays and microwaves for cooking.

Radiation can be either beneficial or harmful, depending on its use and control. Therefore, regulation of certain radioactive sources is necessary so that people are protected from unnecessary or excessive exposures.

Radiation exists naturally everywhere on earth.

U . S . N uc l ear R e g u l ator y C o m m ission 1 What is radiation? adiation is energy given off by matter in the form of rays or Rhigh-speed particles. There are many forms of radiation that are familiar to us. For example, we use light, heat, and microwaves every day. Doctors use x-rays to see inside our bodies. Radio and television waves bring us our favorite shows. All of these are forms of radiation.

Radiation is either ionizing or non-ionizing, depending on how it affects matter. Non-ionizing radiation includes visible light, heat, radar, microwaves, and radio waves. It deposits energy in materials it passes through. Conversely, ionizing radiation, such as x-rays and cosmic rays, is more energetic than non-ionizing radiation. When ionizing radiation passes through material, enough energy is depos- ited to break molecular bonds and cre- ate charged particles. These charged particles can damage plant, animal, and human cells, but they can also be used beneficially. For example, we use ionizing radiation to treat cancer, ster- ilize medical equipment, and in smoke detectors. The U.S. Nuclear Regulatory Commission is the Federal agency that regulates nuclear Smoke detectors with a small materials that produce ionizing radia- amount of radioactive material. tion.

Where does radiation come from? lthough we receive ionizing radiation from both natural and Aartificial sources, most people are not aware of all sources of radiation in their environment.

he NRC is the Federal agency T responsible for regulating the safe uses of radioactive materials for civil- ian purposes in the United States to ensure the protection of public health and safety and the environment.

NRC Headquarters

2 R adiation P rotection The sun and stars send a constant stream of cosmic radiation to Earth, much like a steady drizzle of rain. Differences in elevation, atmospheric conditions, and the Earth’s magnetic field can change the amount of cosmic radiation that we receive. The Earth itself is also a source of ter- restrial radiation. Radioactive materials uranium, radium and thorium exist nat- urally in soil and rock. Essentially all air contains radon, water contains small amounts of dissolved uranium and tho- rium, and all organic matter, both plant and animal, contains radioactive carbon and potassium. All people have internal radiation, mainly from radioactive potassium-40 and carbon-14, inside their bodies from birth. In addition to natural sources, there are artificial or Nuclear medicine man-made sources of radiation. These include medical sources (diagnostic x-rays and nuclear medicine procedures), consumer products (televisions, smoke detectors, luminous watches, and some ceramics), and industrial sources (nuclear power plants and industrial radiography).

What types of radiation are there? s we mentioned before, radiation can be ionizing or non-ioniz- Aing. We are typically more concerned about ionizing radiation because even though it has beneficial uses, it is also potentially harmful if not used correctly. Because of this potential hazard, the NRC strictly regulates commercial and institutional uses of nuclear material, including+ nuclear power plants. Nuclear-power plant There are five major types of ionizing radiation:

 alpha particles  beta particles  gamma rays  x-rays  neutrons - Alpha particles are charged particles with very little penetrating power. They can be blocked by a sheet of paper, skin or a few inches of air. Alpha particles do not usually make anything radioactive.

U . S . N uc l ear R e g u l ator y C o m m ission 3 Materials that emit alpha particles are potentially dangerous when inhaled or swallowed, not because of external exposure. Alpha particles are emitted from naturally-occurring materials such as uranium, thorium, and radium and from man-made elements such as plutonium and americium. Very small amounts of alpha emitters are used in items such as smoke detectors. Beta particles, which are similar to electrons, are lighter and more penetrating than alpha particles, can travel a few feet in the air, and can penetrate the skin. Like alpha particles, they do not usually make things radioactive. A thin sheet of metal or plastic or a block of wood can stop a beta particle. Beta emitters, such as strontium-90, are used in medical applications such as treating eye disease. Gamma rays and x-rays consist of high energy waves that can travel great dis- tances at the speed of light and are very penetrating. In general, neither x-rays nor gamma rays have the ability to make any- thing radioactive. Several feet of concrete or a few inches of more dense material, such as lead, are needed to block these types of radiation. Because of their pene- tration powers, gamma rays, such as from cobalt-60, are often used in medical appli- cations to treat cancer and to sterilize X-rays penetration. medical instruments. X-rays are typically used to provide images of stationary parts of the body such as teeth and bones and are also used in industry to find defects in welds. Neutrons are nuclear particles that are also very penetrating. Neutrons are the only one of the five types discussed here that can make objects radioactive. This process, called neutron activation, is used to pro- duce many of the radioactive sources used in commercial, academic, and medical applications. Neutrons can travel great dis- tances in the air and require very thick hydrogen-containing material (such as con- crete or water) to stop them. Neutron radi- Nuclear power plant reactor core. ation occurs primarily inside a nuclear reactor where many feet of water provide effective shielding. Neutrons are also used in medicine research, and oil exploration.

4 R adiation P rotection Paper Skin Wood Cement

Penetrating Power of Radiation

How is radiation measured?

hether it emits alpha or beta particles, gamma rays or neutrons, Wa quantity of radioactive material is expressed in terms of its radioactivity, or simply its activity, and is measured in curies. Activity represents how many atoms in the material decay in a given time period. The activity of a radioactive material decreases with time. The time it takes for the activity of a radioactive material to decrease by half is called the radioac- Geiger counter. tive half-life. After one half-life, the remaining activity is one half of the original activity. After two half-lives, the remaining activity is one fourth; after three half-lives, one eighth; and so on. Some radioac- tive materials, such as iodine-131, have short half-lives measured in days. Others, such as uranium-238, have half-lives measured in billions of years.

What happens when living things are exposed to radiation? e tend to think of radiation exposure in terms of its effect on W living cells. For low levels of radiation exposure, the effects are so small they may not be detected, because a body can repair damage caused by radiation. The health effects of radiation on living cells may result in three outcomes: (1) injured or damaged cells repair themselves, resulting in no net damage; (2) cells die, much like millions of body cells do every day, being replaced through normal biological processes; or (3) cells incorrectly repair them- selves resulting in a physical change. The exact effect depends on the specific type and intensity of the radiation exposure.

The amount of energy deposited in material by ionizing radiation is called dose. Biological doses are measured in units called rems.

U . S . N uc l ear R e g u l ator y C o m m ission 5 Where curies tell us the radioactivity of a substance, rems tell us the amount of energy that radiation has deposited in an area of living tissue. The likelihood of effects caused by radiation is related to the dose of radiation received, regardless of whether the radiation is of natural or artificial origin. On average, Sources of Radiation Exposure in the United States Americans receive Cosmic (Space) - 5% a dose of about 0.31 Radon and rems (310 milli- Terrestrial Thoron - 37% Industrial and rems) each year (Soil) - 3% Occupational - .1% Internal - 5% from natural or Consumer background radia- Medical Products - 2% tion. Most of this Procedures - exposure comes 36% Nuclear from radon in the Medicine - 12% air with lesser Natural Sources - 50% Manmade Sources - 50% amounts from cos- ~310 millirem (0.31 rem) ~310 millirem (0.31 rem) mic rays and the Source: NCRP Report No.160(2009) Earth itself. We alsoFull report receive is available about on the 0.31NCRP Web rems site at (310 www.NCRPpublications.org. mrem) yearly from man-made sources of radiation, including medical, commercial, and industrial sources. Nuclear medical procedures provide the largest amount of human exposure to man-made radiation. For example, a chest x-ray typically gives a dose of about 0.01 rems (10 mrems) and a CT (full body) scan gives a dose of about 1 rem (1,000 mrem). The average dose is regularly re-evaluated.

A yearly dose of 0.62 rems (620 millirems) from all radiation sources has not been shown to cause humans any harm.

Because radiation from nuclear material is strictly regulated, large doses (~50 rems) of radiation to humans seldom occur. However, high radiation doses, particularly over a short period of time, kill many cells and can damage tissues and organs. Although radiation affects different people in different ways, it is believed that humans exposed to about 500 rems of radiation all at once would likely die without medical treatment. A single dose of 100 rems to a human may cause nausea or skin reddening, but recovery is likely. About 25 rems of radiation can cause temporary sterility in men. If these doses are spread out over time, instead of delivered all at once, their effects tend to be less severe.

How can radiation exposure be reduced? lthough exposure to ionizing radiation carries a risk, it is impos- Asible to completely avoid exposure. We can, however, minimize

6 R adiation P rotection exposure from discrete sources of radiation in three basic ways. They work much the same way as protection against overexposure to the sun.

Time: The concept of time works in two ways. Limiting or minimizing the amount of exposure time will reduce the dose 1from the radiation source. Also, allowing radioactive material as much time as possible to decay before exposure will minimize radiation exposure when that material needs to be handled.

­Distance: Increasing the distance from the radiation source will sharply decrease exposure. The intensity of radiation decreases2 the further you are from the source in the same way that the heat from a fire is less intense the further away you are from it.

Shielding: Inserting a solid material or shield between yourself and a radiation source will greatly reduce the radia- tion3 dose. Barriers of lead, concrete or water provide protection from radiation from gamma rays and neutrons. This is why certain radioactive materials are stored under water or in concrete or lead- lined rooms, and why dentists place a lead blanket on patients receiving x-rays of their teeth.

Less time spent Greater distance from Behind shielding from near source: less source: less radiation source: less radiation radiation received. received. received.

How does NRC HELP protect the public from radiation exposure? adiation and its risks command considerable public attention. RHowever, a system of radiation protection has been developed over many decades as the effects of radiation have become better understood. Specifically, the NRC ensures that users of radioactive materials keep radiation exposures within its dose limits and as low as reasonably achievable. Users must obtain a license from the NRC and be inspected by the NRC to make sure they are following regulations and using radioactive materials safely.

U . S . N uc l ear R e g u l ator y C o m m ission 7 In its standards for protection against radiation, the NRC has requirements for:

 Dose limits for radiation workers and members of the public  Monitoring and labeling radioactive materials  Posting signs in and around radiation areas  Reporting the theft or loss of radioactive material In addition, there are penalties for not following NRC regulations. The NRC requires that radioactive materials be used in a way that limits radiation exposure of individual members of the public to a dose that does not exceed 0.1 rem (100 mrems) in a year. Adults working with radioactive material must be protected so as not to receive more than 5 rems (5,000 mrems) per year. Because workers are exposed to various radiation sources, they are carefully monitored with the use of small instruments called dosimeters. If certain conditions are met, the NRC may enter into an agreement with the governor of a state to turn over authority for regulating radioactive materials to that state. States that meet these conditions and agree to regulate materials using the same standards as the NRC are called Agreement States. Typically, Agreement States regulate all sources of radiation in the state except nuclear power plants, large quantities of certain nuclear material, and any high-level radioactive waste stored in the state. Currently, 34 states have such agreements with the NRC. For more information on radiation protection, please visit our website at: www.nrc.gov and click on the second blue box, Radiation Protection, on the left-hand side of the screen.

8 R adiation P rotection

U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Office of Public Affairs

NUREG/BR-0322, Rev. 1 June 2010­­­­­